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Communication Dans Un Congrès Année : 2002

Controlled Synthesis of Nanoclusters and Nanostructured Oxide Films by Nanosecond and Femtosecond Pulsed Laser Ablation

Résumé

In this communication we present a pulsed laser ablation (PLA) method of synthesis of high quality nanostructured thin films for optoelectronics applications. Contrary to the well-known epitaxial (atom by atom) growth at low oxygen pressure we use a cluster-assisted synthesis of oxide films. Gas phase ZnO, TaO, SiO nanoclusters have been formed during conventional Ultra Violet (λ = 193 nm) or IR femtosecond PLA of sintered targets into binary, O 2 /He or O 2 /Ar, gas mixtures. The role of the first gas is as oxidizing agent and the second one is used for nanocluster cooling and reducing their velocity during condensation and deposition stage. Fundamental aspects of nanoclusters synthesis have been analyzed by reflectron mass spec-trometry (MS) and optical time resolved spectroscopy of the laser induced plume together with structural analysis of solid films by X-ray diffraction, HREM and AFM microscopy. Optical and lasing properties of films have been studied by conventional photoluminescence and excitation spectroscopy using femtosecond lasers. From MS measurements we show that oxide clusters are already formed in vacuum. Clusters with atoms number up to 30 have been registered. The concentration of these clusters strongly increases during synthesis in the surrounding gas. For example, in the case of zinc oxide, we clearly observed four distinct populations: the major one with composition Zn x O x−1 and three minor, oxygen rich, population Zn x O x+1 , Zn x O x+2 and Zn x O x+3. The relative concentration of these initial clusters within the laser induced plume determines the final properties of the film. The total yield of gas formed nanoclusters shows a well pronounced maximum as a function of laser fluence. From all of these results, using the relation between nucleation rate, plume temperature and number of ejected particles, we show a way of the deposition process optimizing. Example of the films properties will be given for ZnO. If the cluster assisted deposition produces homogeneous nanostructured films with cluster size between 5-15 nm , depending on the conditions of the synthesis, for all oxides. ZnO deposits show oriented nanostructures with C axis ⊥ to the substrate, where the substrate were electronic grade c-Al2O3, SiO2 , Si[111] or Si[100]. ZnO films formed under optimized conditions exhibit excellent optical properties with a narrow exciton luminescence band and a strongly reduced defect green band. Finally we demonstrate room temperature ultraviolet laser emission from nanostruc-tured ZnO. Both exciton-exciton and electron-hole plasma emission regimes were observed.
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Dates et versions

hal-02904660 , version 1 (27-07-2020)

Identifiants

  • HAL Id : hal-02904660 , version 1

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W. Marine, I. Ozerov, Alexander V Bulgakov, M. Sentis. Controlled Synthesis of Nanoclusters and Nanostructured Oxide Films by Nanosecond and Femtosecond Pulsed Laser Ablation. IQEC/LAT International Quantum Electronics Conference, Jun 2002, Moscou, Russia. ⟨hal-02904660⟩
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